M2 Junction 5

The M2 junction 5/A249 Stockbury Roundabout in Kent was one of the top 50 national casualty locations on England’s major ‘A’ roads and motorways. The junction was unable to cope with existing traffic flows or support Kent County Council’s plans for economic growth accompanying local regeneration, housing and employment growth .

The road network was redesigned to provide a grade separated junction spanning a new roundabout and a series of six tall retaining walls with a cumulative length of 980m. The challenge was not only the scale of the intervention but also its sensitive location within the Kent Downs Area of Outstanding Natural Beauty (AONB).

Knight Architects’ solution pays homage to the history of local construction where flint, historically a waste material from farmland, was used for wall infill in the construction of buildings and field boundary walls. The perception of the new retaining walls by users looking from up close or from afar, and travelling at low and fast speed, was an important consideration in the design process. This drove a modular design solution using precast panels to achieve a reduction in the use of natural stone of more than 30%, with a significant reduction in cost.